Pharmacokinetics and Indications: Sildenafil citrate is a popular drug used mainly for erectile dysfunction. Sildenafil is a PDE5 inhibitor . Erection is the result of pooling of blood in penile vessels. Tadalafil increases the supply of cGMP in blood vessels by inhibiting PDE which dilates penile blood capillaries and smooth muscle of corpus cavernosum. Sildenafil has a half life of 3-4 hours. It only exerts its effect if there is sexual stimulation, as nitric oxide is only released on sexual stimulation. Sildenafil was first investigated for treatment of hypertension and angina pectoris, but was found to be effective more to achieve and maintain erection. Sildenafil was approved for use in erectile dysfunction in 1988. This drug is metabolized by liver and excreted through kidneys. Main indication of Sildenafil is treatment of erectile dysfunctions due to many reasons for example diabetes mellitus and psychosomatic causes of impotence. Sildenafil has also been approved by FDA for the treatment of pulmonary hypertension. Other indications for which this drug is being studied are altitude sickness and jet lag research. Sildenafil is available in form of 25mg, 50mg and 100mg tablets. The recommended starting dose for erectile dysfunction is 25mg to 100mg OD. This drug should not be used more than once a day for this indication.

Possible Side Effects: Most common side effects are headache, flushing, dyspepsia, nasal congestion, runny nose, photophobia, blurred vision and cyanopsia (seeing everything blue). Other side effects are hypotension, myocardial infarction, cardiac arrhythmias, stroke and priapism. Sudden hearing loss and increased intraocular pressure are also reported. Caution should be used in patients on protease inhibitors and alpha blockers.